Somewhere along Brindcliff Edge Road in Sheffield, you can still see this wonderful infrastructural relic:

That’s a sewer-gas destructor lamp, of which there are maybe a dozen or so remaining in the city, though only a very few of them are a) undamaged, and b) still lit. Destructor lamps took a tricky infrastructural problem (the way in which noxious gases would accumulate in sewer sections near the top of hills) and solved it in a way that had a useful function (mixing said sewer gas with town-gas and burning it to light a street). I have a particular soft spot for this one because of the way it has been incorporated into the wall.